WO2014174800A1

WO2014174800A1 - Acousto-optical imaging device

Info

Publication number: WO2014174800A1
Application number: PCT/JP2014/002134
Authority: WO
Inventors: 卓也岩本; 橋本　雅彦; 寒川　潮; 金子　由利子
Original assignee: パナソニックＩｐマネジメント株式会社
Priority date: 2013-04-22
Filing date: 2014-04-15
Publication date: 2014-10-30

Abstract

An acousto-optical imaging device according to the present invention comprises: an ultrasonic source (1) which outputs ultrasonic waves; an acousto-optical medium unit (2) which has an acoustic opening and into which dispersed ultrasonic waves generated by ultrasonic waves being dispersed inside an object enter inside from the acoustic opening and are propagated; a wedge light source which emits a single color wedge beam that enters the acousto-optical medium unit in non-parallel with respect to the direction of propagation of the dispersed ultrasonic waves; an imaging optical system (3) into which diffracted light enters that is generated by refractive index variation caused in the acousto-optical medium unit by the propagation of the dispersed ultrasonic waves; and a imaging unit (4) which takes an image generated by the diffracted light formed by the imaging optical system and outputs an electrical signal. The wedge beam forms a focal point on a first cross section that is parallel to the propagation direction of the wedge beam and the direction in which the dispersed ultrasonic waves are propagated in the acousto-optical medium unit, and propagates in parallel without forming a focal point on a second cross section which is perpendicular to the cross section, wherein the focal point of the wedge beam on the first cross section is positioned between the acousto-optical medium unit (2) and the imaging optical system (3), and the light intensity of the wedge beam in the direction in which the dispersed ultrasonic waves are propagated in the acousto-optical medium unit increases monotonously according to the distance from the acoustic opening.

Description

Acousto-optic imaging device

The present application relates to an acoustooptic imaging device, and more particularly to an acoustooptic imaging device that acquires an ultrasonic echo obtained from a subject as an optical image.

2. Description of the Related Art As an apparatus that irradiates an object with ultrasonic waves and generates an optical image using scattered waves from the object, an ultrasonic diagnostic apparatus as disclosed in Patent Document 1 is known. In an ultrasonic diagnostic apparatus, an object is transmitted and received using a plurality of ultrasonic transmitting / receiving elements, and the received signals output from each element are delayed and synthesized. Obtain an ultrasonic image.

Such an ultrasonic diagnostic apparatus requires multiple signal processing (delay and synthesis) in order to capture one ultrasonic image. The number of necessary signal processing corresponds to at least the number of pixels of the image. Therefore, in order to photograph an object at high speed using ultrasonic waves, a signal processing circuit having a high-speed and large-scale arithmetic circuit is required. Further, in order to acquire an image with a large number of pixels and high spatial resolution, a large number of ultrasonic transducers having the same transmission / reception characteristics are required. However, it is extremely difficult to construct such a group of transducers.

JP 54-34580 A

The non-limiting exemplary acousto-optic imaging device according to the present invention provides an acousto-optic imaging device capable of imaging the inside of an object without using a signal processing circuit with high calculation processing capability.

An acoustooptic imaging device according to an aspect of the present application includes an ultrasonic source that outputs ultrasonic waves and an acoustic aperture, and scattered ultrasonic waves generated by scattering of the ultrasonic waves inside an object are generated from the acoustic aperture. An acousto-optic medium part that enters and propagates inside, a wedge light source that emits a monochromatic wedge light beam incident on the acousto-optic medium part non-parallel to the propagation direction of the scattered ultrasonic wave, and the scattered ultrasonic wave An imaging optical system in which the generated diffracted light is incident due to a change in refractive index generated in the acousto-optic medium part by propagating and an image of the diffracted light formed by the imaging optical system An imaging unit that outputs a signal, and the wedge light beam is in a first cross section parallel to a propagation direction of the wedge light beam and a propagation direction of the scattered ultrasonic wave in the acoustooptic medium unit. A point is formed and propagates in parallel in the second cross section perpendicular to the cross section without forming a focal point, and the focal point in the first cross section of the wedge light flux is the acoustooptic medium unit, the imaging optical system, and The light intensity of the wedge luminous flux in the direction in which the scattered ultrasonic wave propagates in the acoustooptic medium portion monotonously increases according to the distance from the acoustic aperture.

According to the acoustooptic imaging device according to one aspect of the present invention, it is possible to obtain an image with relatively small luminance unevenness even when an object is imaged using an acoustooptic medium having a large ultrasonic wave propagation attenuation. It becomes.

1 is a diagram schematically illustrating a configuration of an acoustooptic imaging device according to a first embodiment. (A) And (b) is xy sectional drawing and zx sectional drawing which show an example of a structure of the wedge light source of 1st Embodiment. (A) And (b) is xy sectional drawing and zx sectional drawing which show an example of the other structure of the wedge light source of 1st Embodiment. It is a figure which shows a mode that a diffraction image arises by the effect | action of a wedge light beam and an ultrasonic wave. It is a figure which shows the calculation result of the diffraction image in case there is no acoustic attenuation | damping and incident light distribution is uniform. It is a figure which shows the calculation result of a diffraction image in case there exists acoustic attenuation | damping and incident light distribution is uniform. (A)-(d) is a figure which shows the calculation result of the diffraction image in case an acoustic attenuation exists, respectively, and incident light distribution is a 1st, 2nd, 3rd, and 2.5th order function. It is a figure which shows the calculation result of the diffraction image in case there exists acoustic attenuation | damping and incident light distribution is an exponential function. It is a figure which shows an example of the calculation result of a diffraction image when incident light distribution is not uniform without acoustic attenuation. It is a figure which shows the structure of the acousto-optic imaging device by 2nd Embodiment. It is a figure which shows the structure of the acousto-optic imaging device by 3rd Embodiment.

The inventor of the present application examined a method of acquiring an image two-dimensionally or three-dimensionally, instead of obtaining an image by scanning an ultrasonic wave through a tissue inside a subject like a conventional ultrasonic diagnostic apparatus. . As a result, the inventors have conceived that an image of a tissue inside a subject is acquired using an acoustooptic effect that is an interaction between ultrasonic waves and light.

Specifically, as disclosed in Non-Patent Document 1, an acoustic wave is radiated on an object, and an ultrasonic wave transmitted through the object or an ultrasonic wave scattered from the object is propagated in the acoustooptic medium. If the refractive index distribution is formed in the medium and the intensity / phase distribution of transmitted or scattered ultrasonic waves is transferred to the intensity / phase distribution of monochromatic light using the Bragg diffraction generated thereby, the image inside the object is taken as an optical image. It is considered possible.

However, Non-Patent Document 1 only discloses the acoustooptic effect by Bragg diffraction, and there is no suggestion on how to realize imaging of a tissue in a living body by the acoustooptic effect.

The inventor of the present application has examined the technology disclosed in Non-Patent Document 1 in detail, and according to the configuration disclosed in Non-Patent Document 1, the frequency of ultrasonic waves used is as high as 15 MHz or higher. This is because the acousto-optic cell is composed of an aqueous medium, and the conditions under which Bragg diffraction occurs are limited by the relationship between the acoustic velocity of water (about 1500 m / s) and the wavelength of ultrasonic waves. . In a living body, absorption attenuation increases substantially in proportion to the frequency. Therefore, it is preferable to use an ultrasonic wave having a frequency of 10 MHz or less in order to image a deep interior of a subject. Therefore, even if the configuration disclosed in Non-Patent Document 1 is used as it is, it is difficult to obtain an image of the tissue in the body of the subject.

In order to lower the frequency of the ultrasonic wave to be used, it is conceivable that the acoustooptic cell is composed of an acoustooptic medium having a low sound velocity. However, in this case, it has been found that the attenuation of the ultrasonic wave propagating through the acousto-optic cell increases, and the luminance unevenness in the image inside the obtained object increases.

The inventor of the present application has studied such a problem in detail and has come up with a novel acousto-optic imaging device. The outline of one aspect of the acousto-optic imaging device of the present invention is as follows.

The light intensity distribution in the direction of propagation of the scattered ultrasonic waves of the wedge light beam may be defined by an exponential function.

The light intensity distribution in the direction of propagation of the scattered ultrasound of the wedge light beam may be defined by a linear function with respect to the distance from the acoustic aperture.

The light intensity distribution in the direction of propagation of the scattered ultrasonic waves of the wedge light beam may be defined by a quadratic function with respect to the distance from the acoustic aperture.

The light intensity distribution in the direction in which the scattered ultrasound propagates of the wedge light beam may be defined by a cubic function with respect to the distance from the acoustic aperture.

The distribution of light intensity in the direction of propagation of the scattered ultrasonic wave of the wedge luminous flux is defined by a power function of the distance from the acoustic aperture or a sum of power functions, and a power exponent of the power function is an arbitrary real number. Also good.

The wedge light source includes a laser light source that emits a monochromatic light wave, a magnifying optical system that emits a monochromatic light wave from the laser light source and emits an enlarged plane wave light beam, and a plane wave light beam that emerges from the magnifying optical system. Light transmittance that is disposed between the cylindrical lens, the laser light source, and the magnifying optical system, or between the magnifying optical system and the acoustooptic medium unit, and has a distribution in the direction in which the scattered ultrasound propagates The cylindrical lens has a refractive power that focuses on the first direction on a plane perpendicular to the propagation direction of the incident plane wave light beam, and a second direction perpendicular to the first direction. The first lens lens may have no refractive power, and the first direction of the cylindrical lens may be parallel to the direction in which the scattered ultrasound propagates.

The optical element may be a neutral density filter.

The optical element may be a liquid crystal element capable of controlling transmittance in a direction in which the scattered ultrasonic wave propagates.

The wedge light source is a laser light source that emits a monochromatic light wave, and an enlarged optical system that emits an expanded plane wave light beam by receiving the monochromatic light wave from the laser light source, and is distributed in a direction in which the scattered ultrasonic wave propagates A magnifying optical system including a lens configured to obtain an intensity having a cylindrical lens, and a cylindrical lens on which a plane wave light beam emitted from the magnifying optical system is incident. The cylindrical lens propagates the incident plane wave light beam. On the surface perpendicular to the direction, the first direction has a refractive power for focusing, the second direction perpendicular to the first direction has no refractive power, and the first direction of the cylindrical lens It may be parallel to the direction in which the sound wave propagates.

The acousto-optic imaging device may further include an optical aperture disposed between the magnifying optical system and the cylindrical lens.

The ultrasonic source and the acousto-optic medium part are directed to the object so that the generated scattered ultrasonic wave enters the acousto-optic medium part from the acoustic aperture when the ultrasonic wave passes through the object. It may be arranged.

The ultrasonic source and the acousto-optic medium part are directed to the object so that the generated scattered ultrasound is incident on the acousto-optic medium part from the acoustic aperture by reflecting the ultrasonic wave on the object. It may be arranged.

The acousto-optic imaging device includes an incident-side mirror that reflects a wedge light beam emitted from the wedge light source and enters the acousto-optic medium unit, and reflects diffracted light generated in the acousto-optic medium unit to reflect the imaging optics. An exit-side mirror that enters the system may be further included.

The acousto-optic imaging device receives the electrical signal from the imaging unit, and performs signal processing for adjusting the image so that luminance unevenness in the direction in which the scattered ultrasound propagates on the image of the captured image is reduced. A part may be further provided.

(First embodiment)
Hereinafter, a first embodiment of the acoustooptic imaging device 100 of the present invention will be described. FIG. 1 is a schematic diagram illustrating a configuration of an acousto-optic imaging device 100 according to the first embodiment.

(Configuration of acousto-optic imaging device 100)
The acousto-optic imaging device 100 includes a wedge light source 1, an acousto-optic medium unit 2, an imaging optical system 3, an imaging unit 4, and an ultrasonic source 5. Hereinafter, as shown in FIG. 1, the propagation direction (optical axis) of the wedge light beam 8 is the z axis, and the direction perpendicular to the acoustic aperture 203 that is the surface where the object 6 and the acoustooptic medium unit 2 are in contact is the y axis. In the following description, the direction perpendicular to the paper plane, which is the direction perpendicular to the y-axis and the z-axis, is defined as the x-axis.

The ultrasonic source 5 is arranged so as to be in contact with the object 6 at the time of imaging, and outputs the ultrasonic wave 7 inside the object 6. The ultrasonic wave 7 propagates inside the object 6, and when the part 6 a having different acoustic characteristics (impedance) exists in the object 6, the scattered ultrasonic wave 7 a is generated in the part 6 a. The acoustooptic medium unit 2 is disposed so as to be in contact with the object 6 through the acoustic aperture 203 at the time of imaging, and takes in the scattered ultrasonic waves 7 a generated in the object 6. Scattered ultrasonic waves 7 a generated in the object 6 are taken into the acoustooptic medium unit 2, and scattered ultrasonic waves 7 b having information on the object 6 in intensity and phase distribution propagate through the acoustooptic medium 201.

The wedge light source 1 emits a wedge light beam 8 toward the acousto-optic medium unit 2. The wedge light beam 8 converges in the y direction in FIG. 1 to have a focal point, and propagates in parallel without converging in the x direction. Further, the focal point of the wedge light beam 8 is located on the opposite side of the wedge light source 1 across the acoustooptic medium unit 2, that is, between the acoustooptic medium unit 2 and the imaging optical system 3. Further, the light intensity of the wedge light beam 8 in the y direction monotonously increases according to the distance from the acoustic aperture 203.

When the scattered ultrasonic wave 7b propagates through the acousto-optic medium unit 2, the scattered ultrasonic wave 7b is a dense wave, so that a coarse-dense distribution is generated in the acousto-optic medium unit 2. This density distribution functions as a diffraction grating for the wedge light beam 8, and a −1st order diffracted light beam 8a, a 0th order diffracted light beam 8b, and a + 1st order diffracted light beam 8c are generated. The −1st order diffracted light beam 8 a and the + 1st order diffracted light beam 8 c are focused on the focal plane 9 to form an image of the object 6. Here, the focal plane 9 refers to a plane (xy plane) that passes through the focal point of the wedge beam 8 and is perpendicular to the propagation direction of the wedge beam 8.

The image formed on the focal plane 9 is incomplete and forms an image in the direction in which the wedge beam 8 is converged (y direction), but in the direction in which the wedge beam 8 is propagated in parallel (x direction). The image is not formed. The imaging optical system 3 is disposed at a position facing the wedge light source 1 with the acousto-optic medium unit 2 interposed therebetween. The −1st order diffracted light beam 8a and the + 1st order diffracted light beam 8c transmitted through the acoustooptic medium unit 2 enter the imaging optical system 3, and are also converged in the x direction by the imaging optical system 3 to form an image. That is, an incomplete image of the object 6 formed by the −1st order diffracted light beam 8 a and the + 1st order diffracted light beam 8 c is formed as a complete image on the image forming surface 91 by the image forming optical system 3. The imaging unit 4 captures an image of the −1st order diffracted light beam 8a or + 1st order diffracted light beam 8c formed by the imaging optical system 3, and converts the image into an electrical signal. Hereinafter, each component will be described in detail.

(Wedge light source 1)
The wedge light source 1 emits a wedge light beam 8 of monochromatic light. As shown in FIG. 2A, the wedge light beam 8 is focused on the focal plane 9 in the yz plane (first cross section) parallel to the z direction in which the wedge light beam 8 propagates and the y direction in which the scattered ultrasonic waves propagate. Finally, as shown in FIG. 2B, in the xz plane (second cross section), the light propagates in parallel and does not focus. Since the wedge light beam 8 propagates in the z direction, it can be said that it converges in the y direction and does not converge in the x direction. The position of the focal plane 9 of the wedge light beam 8 is located opposite to the wedge light source 1 with the acoustooptic medium unit 2 interposed therebetween, that is, between the acoustooptic medium unit 2 and the imaging optical system 3. Further, the light intensity distribution in the xy section of the wedge light beam 8 is not uniform in the y direction in the acoustooptic medium unit 2 but has a distribution. Specifically, the light intensity increases as the distance from the y-axis acoustic aperture 203 increases. In other words, the light intensity in the y direction increases monotonously according to the distance from the acoustic aperture 203. The light intensity distribution in the y direction of the wedge light beam 8 may be defined by a linear function, or may be defined by an n-order function such as a quadratic function or a cubic function. Further, it may be defined by an exponential function.

The wedge light source 1 includes, for example, a laser light source 10, a magnifying optical system 11, an optical aperture 12, a first cylindrical lens 13, and a neutral density filter 14, as shown in FIGS. 2 (a) and 2 (b). The laser light source 10 emits a monochromatic light wave 81 and enters the magnifying optical system 11. The magnifying optical system 11 enlarges the diameter of the monochromatic light wave emitted from the laser light source 10 and emits a plane wave light beam 82 having the enlarged diameter. The plane wave light beam 82 passes through the optical aperture 12 and enters the first cylindrical lens 13 via the neutral density filter 14. At this time, the plane wave light beam 82 has a light intensity distribution in the y direction by passing through the neutral density filter 14 having a transmittance distribution in the y direction. By using the neutral density filter 14 whose transmittance increases monotonously in accordance with the distance from the acoustic aperture 203 in the y direction, the plane wave light beam 83 transmitted through the neutral density filter 14 is transmitted from the acoustic aperture 203 in the y axis direction. The light intensity can be monotonously increased according to the distance.

The cylindrical lens 13 is set so that the plane wave light beam 83 is focused on the focal plane 9 after passing through the acoustooptic medium unit 2 in the y direction. The plane wave light beam 83 having no refractive power in the x direction and passing through the magnifying optical system 11 passes through the acoustooptic medium unit 2 while being parallel, and does not form an image on the focal plane 9. Thereby, the wedge light flux 8 whose light intensity in the y direction monotonously increases according to the distance from the acoustic aperture 203 is obtained.

Note that the wedge light source 1 is not necessarily configured as shown in FIG. 2, and the position of the neutral density filter 14 is not limited to between the magnifying optical system 11 and the cylindrical lens 13. For example, as shown in FIG. 3A, the neutral density filter 14 may be between the cylindrical lens 13 and the acoustooptic medium unit 2.

In addition, if the wedge light beam 8 has a characteristic that the light intensity in the y direction monotonously increases according to the distance from the acoustic aperture 203, such a light intensity distribution is realized by an optical element other than the neutral density filter 14. May be. For example, a liquid crystal element capable of controlling the transmittance in the y direction may be used instead of the neutral density filter 14. Further, the monochromatic light wave emitted from the laser light source 10 may have a desired light intensity distribution in the y-axis direction in advance. For example, as disclosed in Japanese Patent Application Laid-Open Nos. 2012-168328 and 2012-022252, a monochromatic light wave emitted from the laser light source 10 is transmitted through an optical element such as an aspheric lens so that light in the y direction can be obtained. An intensity distribution may be realized.

(Ultrasonic source 5)
The ultrasonic source 5 is disposed in contact with the object 6 during imaging. The ultrasonic source 5 receives a signal from the ultrasonic signal source 51 and makes the object 6 enter the object 6 with continuous waves or pulsed ultrasonic waves 7 having the same sine waveform. The ultrasonic wave 7 composed of a plurality of waves having the same sine waveform means an ultrasonic wave having a time waveform in which a sine waveform having a constant amplitude and frequency is continuously or continuously for a fixed time. Moreover, the ultrasonic wave 7 irradiates the area of the object 6 to be imaged with a substantially uniform illuminance. Note that the ultrasonic wave 7 incident from the ultrasonic wave source 5 to the object 6 may not be a plane wave.

When using pulsed ultrasonic waves 7, the duration of the time waveform is preferably set to be equal to or greater than the reciprocal (cycle) of the carrier frequency.

The ultrasonic wave 7 incident on the object 6 by the ultrasonic wave source 5 is not limited to an acoustic signal having a sine wave as a carrier wave, but is an ultrasonic signal composed of a repetitive signal having a waveform other than a sine wave such as a square wave or a sawtooth wave. Also good. Note that the adhesion between the ultrasonic source 5 and the object 6 may be improved by using an alignment material such as an ultrasonic gel so that the ultrasonic wave 7 output from the ultrasonic source 5 is efficiently incident into the object 6. .

(Object 6)
The object 6 is made of a material whose ultrasonic wave propagation attenuation is not extremely large. An example of the object 6 is a living body. In this case, the portion 6a may be a tissue or an organ in the object 6. The object 6 may be a liquid such as water, and the portion 6a may be another object arranged in the liquid.

(Ultrasonic 7)
The ultrasonic wave 7 incident on the object 6 propagates through the object 6. When there is a portion 6a having different acoustic characteristics from the substance constituting the object 6 in the object 6, when the ultrasonic wave 7 is reflected or transmitted through the portion 6a, a scattered ultrasonic wave 7a having the same frequency is generated. The scattered ultrasonic wave 7 a is incident on the acoustooptic medium unit 2 through the acoustic aperture 203 and propagates inside the acoustooptic medium unit 2. The scattered ultrasonic wave 7 b propagating through the acousto-optic medium unit 2 has intensity and phase distribution reflecting the information of the object 6.

(Acousto-optic medium part 2)
The acoustooptic medium unit 2 includes an acoustooptic medium 201 and a cell 202, and the acoustooptic medium 201 is included in the cell 202. The acoustooptic medium unit 2 is disposed so as to be in contact with the object 6 at the acoustic aperture 203 when the object 6 is photographed. By arranging the acoustic aperture 203 in contact with the object 6, the scattered ultrasonic wave 7 a from the object 6 is taken into the acoustooptic medium unit 2. In order to efficiently propagate the scattered ultrasonic wave 7 a into the acoustooptic medium unit 2, a matching material such as an ultrasonic gel or an acoustic matching layer is arranged between the object 6 and the acoustooptic medium unit 2. Also good.

The scattered ultrasound 7b propagates in the y-axis direction in FIG. This direction is perpendicular to the surface constituting the acoustic aperture 203 and is the normal direction of the acoustic aperture 203 when the scattered ultrasonic wave 7 a is incident on the acoustic aperture 203 perpendicularly.

Since the scattered ultrasound 7b is a longitudinal wave, when the scattered ultrasound 7b propagates through the acoustooptic medium 201, the sound pressure distribution of the acoustooptic medium 201, that is, the refractive index distribution that matches the wavefront of the scattered ultrasound 7b is acoustooptic. It is generated in the medium 201. At a certain moment, the refractive index distribution generated in the acousto-optic medium 201 becomes a sinusoidal diffraction grating that is repeated at the wavelength of the ultrasonic wave.

When the wedge light beam 8 is incident non-parallel to the propagation direction of the scattered ultrasonic wave 7b, the wedge light beam 8 is diffracted by the diffraction grating formed by the refractive index distribution in the acoustooptic medium 201, and a diffracted light beam is generated. In FIG. 1, only the −1st order diffracted light beam 8a, the 0th order diffracted light beam 8b, and the + 1st order diffracted light beam 8c are shown for simplicity. In general, diffracted light includes Bragg diffracted light and Raman-Nath diffracted light. In the Bragg region where Klein Cook's parameter Q satisfies Q >> 1, Bragg diffracted light is the main diffracted light. In this case, the diffracted light to be generated is only the −1st order diffracted light beam 8a, the 0th order diffracted light beam 8b, and the + 1st order diffracted light beam 8c, and light energy loss is small because no high order diffracted light is generated. For this reason, if it is operated in the Bragg region, the acousto-optic imaging device of the present embodiment can observe the inside of the object with high sensitivity. At this time, the brightness of the diffracted light is proportional to the amount of change in the refractive index of the diffraction grating, that is, the sound pressure of the ultrasonic waves. The Klein Cook parameter Q can be expressed by the following equation.

Here, L represents the interaction length between the ultrasonic wave and the light wave, λ represents the wavelength of the light wave, f represents the frequency of the ultrasonic wave, n represents the refractive index, and V represents the speed of sound. However, the acousto-optic imaging device of the present embodiment may be operated under a diffraction condition mainly including Raman-Nath diffracted light.

The scattered ultrasonic wave 7 b continues to propagate through the acousto-optic medium unit 2 even after contacting the wedge light beam 8. However, if the light is reflected at the end of the acousto-optic medium portion 2 and again comes into contact with the wedge light beam 8, there is a possibility that the acquisition of the image is hindered. For this reason, a sound wave absorption end 204 may be provided at the end of the acousto-optic medium unit 2 opposite to the acoustic opening 203 to suppress reflection of the scattered ultrasonic waves 7b.

The cell 202 and the acousto-optic medium 201 are made of a material that is transparent with respect to the wavelength of the light wave output from the laser light source 10 so that the wedge light beam 8 can enter. For example, a glass cell can be used as the cell 202.

As the acousto-optic medium 201, water transparent to the wavelength of the light wave output from the laser light source 10, a fluorine-based liquid material, a silica nanoporous material, or the like can be used. When a high-resolution image is acquired by the acousto-optic imaging device 100, it is preferable to use a medium with the lowest possible sound velocity as the acousto-optic medium 201. In particular, when the object is a living body, it is preferable to use an ultrasonic wave having a frequency of 10 MHz or less in order to suppress attenuation due to absorption of the ultrasonic wave propagating through the object. In this case, since Bragg diffraction occurs, it is preferable to use a medium having a lower sound velocity than water. More specifically, it is preferable to use a fluorinated liquid material. For example, the speed of sound of water is 1500 m / sec, whereas the speed of sound of NovecTM 7200 (hydrofluoroether) manufactured by Sumitomo 3M Limited is 630 m / sec. Fluorine-based liquid materials such as Novec ™ 7000, Novec ™ 7100, Novec ™ 7200, Novec ™ 7300, Fluorinert TMFC-72 and FC-3283 are also materials having a low sound velocity. Further, the sound speed of the silica nanoporous material is as low as 50 to 250 m / sec, which is a preferable material for use as the acoustooptic medium 201.

(

Diffraction beam

8a, 8c)
The −1st order diffracted light beam 8 a and the + 1st order diffracted light beam 8 c generated by the action of the scattered ultrasonic wave 7 b having information inside the object 6 and the wedge light beam 8 in the acoustooptic medium 201 are located at the focal point of the wedge light beam 8. In the focal plane 9 perpendicular to the propagation direction of the wedge beam, the light converges in the y direction and forms an optical image of the object 6. However, the optical image of the object 6 generated at this time does not form an image in the x direction. As will be described in detail below, an optical image of the object 6 on the xz plane is generated on the focal plane 9 without forming an image in the x direction.

(Imaging optical system 3)
The −1st order diffracted light beam 8 a and the + 1st order diffracted light beam 8 c that have passed through the acoustooptic medium unit 2 enter the imaging optical system 3. The −1st-order diffracted light beam 8a and the + 1st-order diffracted light beam 8c pass through the imaging optical system 3, thereby forming an image in the x direction and on the imaging surface 91 in both the x direction and the y direction. A complete optical image forming the image is produced.

The imaging optical system 3 includes, for example, a cylindrical lens 3a and a cylindrical lens 3b as shown in FIG. The cylindrical lens 3a is arranged so as to have a refractive power in the y direction and no refractive power in the x direction. The cylindrical lens 3b is arranged so as to have a refractive power in the x direction and no refractive power in the y direction.

Similarly, the 0th-order diffracted light beam 8 b that has passed through the focal plane 9 is converged in the y direction by the cylindrical lens 3 a of the imaging optical system 3 and focused in the y direction on the imaging plane 91. Further, the light is converged in the x direction by the cylindrical lens 3 b and focused on the image plane 91.

(Imaging unit 4)
The imaging unit 4 takes an optical image of the −1st order diffracted light beam 8a or the + 1st order diffracted light beam 8c on the imaging surface 91 and converts it into an electrical signal. Thereby, the information inside the object 6 can be detected by ultrasonic waves and acquired as an optical image. As will be described below, the imaging unit 4 captures an optical image of the xz plane in an arbitrary y direction inside the object 6. Optical images on the xz plane at different y-direction positions can be obtained by shifting the time. Therefore, for example, if an electrical signal from the imaging unit 4 indicating an optical image of the xz plane at different y-direction positions is stored, a three-dimensional optical image inside the object 6 can be displayed on a display device or the like. Is possible.

The light-shielding unit 15 may block the 0th-order diffracted light beam 8b or the other diffracted light beam that is not received so that only the −1st-order diffracted light beam 8a or the + 1st-order diffracted light beam 8c is incident on the imaging unit 4.

The imaging unit 4 is a solid-state imaging element such as a CCD element or a CMOS element, for example, and detects the light intensity distribution of the diffraction image by the −1st order diffracted light beam 8a or the + 1st order diffracted light beam 8c as an optical image and converts it into an electrical signal. Convert.

(About uneven brightness of optical image)
Next, the luminance unevenness of the optical image obtained in the imaging unit 4 of the acoustooptic imaging device 100 according to the present embodiment will be described with reference to specific examples.

In the following embodiments, the object 6 is a living body, and the ultrasonic source 5 emits a 2.5 MHz continuous ultrasonic wave. A rectangular parallelepiped cell made of Tempax glass is used as the cell 202 of the acoustooptic medium unit 2, and the thickness of the glass constituting the cell is 1.1 mm. The cell 202 is filled with a silica nanoporous material having an acoustic velocity of 100 m / s as the acoustooptic medium 201. Since the silica nanoporous material has a relatively low sound velocity, the wavelength of the ultrasonic wave in the acoustooptic medium 201 is shortened, and the diffraction angle can be increased. Tempax glass and silica nanoporous material are transparent to He—Ne laser light having a wavelength of 633 nm, which will be described later. As the laser light source 10, a He—Ne laser having a wavelength of 633 nm is used. When a He—Ne laser having a wavelength of 633 nm is used, first-order Bragg diffracted light is generated at a diffraction angle of 0.45 ° by a diffraction grating in a silica nanoporous material generated by 2.5 MHz ultrasonic waves.

FIG. 4 shows that a plane wave scattered ultrasonic wave 7 a is incident on the acoustooptic medium unit 2, and the incident scattered ultrasonic wave 7 b comes into contact with the wedge light beam 8, resulting in a diffraction angle θ _B = 0.45 °. It shows how the + 1st order diffracted light beam 8c is generated. The scattered ultrasonic wave 7b having information on the object in the object 6 in amplitude and phase acts on the wedge light beam 8 and diffracts, whereby an optical image of the object 6 is obtained in the + 1st order diffracted light beam 8c. FIG. 4 shows a state where a plane wave ultrasonic wave 7 a having a uniform intensity is incident on the acoustooptic medium unit 2. The incidence of a plane wave ultrasonic wave 7 a having a uniform intensity corresponds to the presence of a uniform object within the viewing angle of the object 6 and the ultrasonic wave 7 being uniformly scattered. In this case, the light intensity of the obtained diffraction image is preferably uniform.

Hereinafter, the light intensity distribution of the diffracted light beam 1b generated when the wedge light beam 8 contacts the scattered ultrasonic wave 7b is obtained by calculation. For simplicity in calculation, the wedge light beam 8 is treated as a collection of n light beams that pass through the focal point on the focal plane 9 as shown in FIG.

The diffraction image generated when the scattered ultrasonic wave 7b and the wedge light beam 8 contact each other in the acousto-optic medium 201 is a sum of diffracted light beams generated by diffracting each light beam by the scattered ultrasonic wave 7b. 4, z coordinate z _0, z _m, the light beams diffracted by the scattered ultrasonic 7b are perpendicular plane leave the z-axis is z _e are each point on z 'axis on the focal plane 9 It shows how an image is formed by z ₀ ′, z _m ′, and z _e ′. The z ′ axis is parallel to and opposite to the y axis. The image formed on the focal plane 9 is an incomplete image that forms an image in the y direction but does not form an image in the x direction. This image is converged in the x direction by the imaging optical system 3 to form an image of the object 6 on the imaging surface 91. As described above, the optical image of the xz plane of the object 6 is generated on the focal plane 9 without forming an image in the x direction.

Note that the time at which the scattered ultrasonic wave 7b obtained from the object 6 reaches the acousto-optic medium part 2 varies depending on the position of each part of the object 6 in the y-axis direction. For example, the scattered ultrasonic wave 7 a ′ from the portion of the object 6 that is far from the acoustic aperture 203 of the acoustooptic medium unit 2 in the y-axis direction is delayed from the scattered ultrasonic wave 7 a by the acoustic of the acoustooptic medium unit 2. The opening 203 is reached. The scattered ultrasonic wave 7a ′ propagates as the scattered ultrasonic wave 7b ′ in the acousto-optic medium part 2 with a delay from the scattered ultrasonic wave 7b, thereby generating a + 1st order diffracted light beam 8c ′ later than the + 1st order diffracted light beam 8c. To do. In this way, optical images of the object 6 in the xz plane at an arbitrary depth in the y-axis direction are formed at different times. That is, information in the y-axis direction of the object 6 is included in the optical image formed on the focal plane 9 after being converted on the time axis.

The light intensity distribution in the y direction of the image on the imaging plane 91 is determined by the light intensity distribution in the y direction of the image of the −1st order diffracted light beam 8a or the + 1st order diffracted light beam 8c on the focal plane 9. Therefore, in order to examine the uniformity of the light intensity distribution on the imaging plane 91, the light intensity distribution of the image on the focal plane 9 may be examined.

First, consider the case where the wedge beam 8 has a uniform intensity in the y direction. Each diffracted light intensity I _k is shown in Formula (1).

The sound pressure P of the scattered ultrasonic wave 7b at the position (y, z) in the acousto-optic medium 201 is expressed as shown in Expression (2).

Here, α indicates the propagation attenuation rate of the ultrasonic wave in the acoustooptic medium 201, and P ₀ is the scattered light ray I ₁ closest to the acoustic aperture 203 at the position (z ₀ ) where the wedge light beam 8 is incident on the acoustooptic medium 201. The sound pressure of the ultrasonic wave at the position in contact with the ultrasonic wave 7b is shown.

The light intensity distribution I _image (z ′) of the diffracted image at the focal plane 9 is expressed by the following equation (3).

Here, J ₁ represents the first-order Bessel function, Δn represents the amount of change in the refractive index caused by the sound pressure of 1 Pa, and λ represents the wavelength of the wedge light beam 8.

The sound pressure P ₀ can be changed by changing the intensity of the ultrasonic wave 7 incident from the ultrasonic source 5. For example, in the case of using a silica nanoporous material with a wavelength λ = 633 nm of the laser light source 10 and a refractive index change Δn = 1.0 × 10 ^{−7 for} the acoustooptic medium 201, if the sound pressure P ₀ is 10070 Pa, the formula ( 3) becomes as shown in Equation (4).

Even if the acousto-optic medium 201 is another material such as water or a fluorinated liquid material, the diffracted light intensity distribution is expressed by the equation (4) by adjusting the sound pressure P _0. Uses equation (4).

Position incident on the acousto-optic medium 201 (z ₀₎ position 5mm height H of the

wedge beam

8, 10 mm width L of the acousto-optic medium 201, the wedge beam 8 from the acousto-optic medium 201 emits at (z _e) If the distance from the focal plane 9 to δL = 1 mm, the z-coordinate and y-coordinate of the light ray I _k can be expressed by the relationship of the equation (5).

First, consider the case where the ultrasonic wave propagation attenuation rate α is very small and can be ignored. For example, this is the case when water is used as the material of the acousto-optic medium 201 and the ultrasonic frequency is about 10 MHz or less. In the calculation, the number of rays n of the wedge beam 8 was set to 100. FIG. 5 shows the calculation result of the light intensity distribution of the diffraction image when α = 0. The light intensity distribution on the vertical axis in FIG. 5 is normalized so that the light intensity at Z ₀ ′ is 1, but from this calculation result, it can be seen that the diffraction image intensity is uniformly distributed. It can be confirmed that a good image can be obtained when the ultrasonic wave propagation attenuation rate α is very small.

Next, let us consider a case where the ultrasonic wave propagation attenuation rate α is large. For example, when a silica dry gel or a fluorinated liquid material is used as the material of the acousto-optic medium 201, there is a large propagation attenuation compared to the case where water is used. When the propagation attenuation factor α was measured at a frequency of 2.5 MHz in the silica dry gel used as the acoustooptic medium 201 in this example, it was about −1.24 Np / mm. The calculation result of the light intensity distribution of the diffraction image in this case is shown in FIG. In this calculation result, the minimum value of the light intensity of the diffracted image is about 8% of the maximum value, and it can be confirmed that the intensity distribution of the diffracted light is not uniform and uneven. As a result, when the propagation attenuation rate α of the ultrasonic wave is large, even if the object 6 is a uniform object, the intensity distribution of the diffraction image is not uniform, and the image of the object 6 is not included in the obtained image. This suggests that irrelevant luminance unevenness occurs.

In the acousto-optic imaging device 100 of the present embodiment, the y-direction of the wedge beam 8 is reduced in order to reduce the luminance unevenness of the image that is generated regardless of the actual state of the object 6 when the ultrasonic wave propagation attenuation in the acousto-optic medium 201 is large. A distribution is provided for the light intensity at.

In the above calculation, the intensity of each light beam I _k constituting the wedge light beam 8 is set to a constant value as shown in the equation (1), but in the y direction, the equations (6), (7), (8), As shown in the equation (9), a one-light intensity distribution of the diffraction image is calculated in the case where the function is expressed by an N-order function (N is an arbitrary real number) and the exponential function shown in the equation (10).

The calculation results of the respective light intensity distributions are shown in FIGS. 7 (a), (b), (c), (d) and FIG. Expressions (6) to (10) are all simple increase functions, and light rays that are farther away from the acoustic aperture 203 have a higher light intensity distribution. 7 (a), (b), (c), and (d), the maximum and minimum values of the diffracted light intensity are obtained when any of the distributions of the equations (6) to (9) is adopted as compared with FIG. It can be seen that the difference between the values is small, and the unevenness of the light intensity distribution of the diffraction image is reduced. Moreover, it can be confirmed from the calculation result of FIG. 8 that the unevenness of the light intensity is reduced in the diffraction image of the wedge light beam even when the light intensity distribution in the form of exponential function is adopted.

In FIG. 7, the light intensity distribution unevenness of the diffraction image is most reduced when Expression (9) is adopted as the light intensity distribution of the wedge luminous flux 8, but the acoustooptics having different ultrasonic propagation attenuation rates α are used. When the medium 201 is assumed, the formula (9) is not necessarily preferable. When the acousto-optic medium 201 having a different ultrasonic propagation attenuation rate α is used, it is preferable to perform a similar calculation to design a suitable light intensity distribution.

In order to further reduce the unevenness of the light intensity distribution, the electrical signal of the optical image of the object 6 obtained by the imaging unit 4 may be corrected. For example, the acoustooptic imaging device 100 may further include a signal processing unit 21 that receives an electrical signal from the imaging unit 4 and corrects luminance unevenness in the y direction in the optical image of the object 6 represented by the electrical signal. Specifically, for example, the signal processing unit 21 is represented by a function that monotonously increases the luminance from Z ₀ to Z _e so that the light intensity distribution shown in FIG. The luminance information of the electric signal may be multiplied by the coefficient.

When the propagation attenuation of the ultrasonic wave in the acousto-optic medium 201 is small, even if the wedge light beam 8 has a light intensity distribution, the light intensity distribution does not cause uneven brightness. In the case where the light intensity distribution is provided in the wedge light beam 8 as in the formulas (6) to (10), a diffraction image in the case where a material with small propagation attenuation of ultrasonic waves such as water is used as the acoustooptic medium 201. The light intensity distribution was calculated. As an example of the calculation result, FIG. 9 shows the calculation result when the light intensity distribution of the wedge light beam 8 is expressed by the equation (8). It can be seen from this calculation that even if the wedge light beam 8 has a light intensity distribution when the propagation attenuation of the ultrasonic wave is small, the light intensity distribution is not uneven in the diffraction image. This is the same when any other light intensity distribution is adopted.

Therefore, in the acousto-optic imaging device of the present embodiment, the acousto-optic medium 201 is not only a material having a large ultrasonic propagation attenuation, such as a silica nanoporous material or a fluorine-based liquid material, but also a water having a small ultrasonic propagation attenuation. It can be said that it is also possible to use.

Thus, according to the acousto-optic imaging device of the present embodiment, it is possible to obtain an optical image with reduced luminance unevenness even when the ultrasonic wave propagation attenuation rate α in the acousto-optic medium 201 is large. In addition, since information inside the object is photographed as a two-dimensional or three-dimensional optical image using ultrasonic waves, the inside of the object can be photographed without using a signal processing circuit with high calculation processing capability. .

(Second Embodiment)
Hereinafter, a second embodiment of the acousto-optic imaging device of the present invention will be described. FIG. 10 is a schematic diagram showing the configuration of the acousto-optic imaging device 101 of the present embodiment.

(Configuration of acousto-optic imaging device 101)
The acoustooptic imaging device 101 includes a wedge light source 1, an acoustooptic medium unit 2, an imaging optical system 3, an imaging unit 4, and an ultrasonic source 5.

The wedge light source 1 emits a wedge light beam 8, and the wedge light beam 8 enters the acousto-optic medium unit 2. As in the first embodiment, the wedge light beam 8 has a strong light intensity distribution in the direction away from the acoustic aperture 203 in the y direction.

The imaging optical system 3 is disposed on the opposite side of the wedge light source 1 with the acoustooptic medium unit 2 interposed therebetween, and the −1 diffracted beam 8a, the 0 diffracted beam 8b, and the +1 diffracted beam 8c transmitted through the acoustooptic medium unit 2. Enters the imaging optical system 3. The imaging unit 4 detects a −1 diffracted light beam 8 a or a +1 diffracted light beam 8 c that has passed through the imaging optical system 3.

In the present embodiment, at the time of imaging, the ultrasonic source 5 is disposed so as to be in contact with the object 6 and outputs the ultrasonic wave 7 inside the object 6. The acoustooptic medium unit 2 is disposed on the opposite side of the ultrasonic wave 7 with the object 6 interposed therebetween, and the scattered ultrasonic wave 7 a ″ transmitted through the object 6 enters the acoustooptic medium unit 2 from the acoustic aperture 203.

As in the first embodiment, in the acousto-optic medium unit 2, the wedge light beam 8 incident from the wedge light source 1 acts on the scattered ultrasonic wave 7b taken into the acousto-optic medium unit 2, thereby -1st order diffraction. A light beam 8a, a 0th-order diffracted light beam 8b, and a + 1st-order diffracted light beam 8c are generated. The diffracted

light beams

8a, 8b, and 8c that have passed through the acousto-optic medium unit 2 are incident on the imaging optical system 3, and only the −1st order diffracted light beam 8a or the + 1st order diffracted light beam 8c are incident on the imaging unit 4 to form an image. .

According to the acousto-optic imaging device 101 of the present embodiment, the ultrasonic source 5 and the acousto-optic medium unit 2 are arranged at positions facing each other with the object 6 interposed therebetween, thereby imaging using the transmitted ultrasound of the object 6. Can be done.

(Third embodiment)
Hereinafter, a third embodiment of the acousto-optic imaging device of the present invention will be described. FIG. 11 is a schematic diagram illustrating the configuration of the acousto-optic imaging device 102 of the present embodiment.

(Configuration of acousto-optic imaging device 102)
The acoustooptic imaging device 102 includes a wedge light source 1, an acoustooptic medium unit 2, an imaging optical system 3, an imaging unit 4, an ultrasonic source 5, an incident side mirror 16a, and an output side mirror 16b.

The wedge light beam 8 emitted from the wedge light source 1 is reflected by the incident side mirror 16a and enters the acoustooptic medium unit 2. The wedge light beam 8 has a light intensity that increases in a direction away from the acoustic aperture 203 on the incident surface that is incident on the acoustooptic medium unit 2. The exit side mirror 16b is disposed on the opposite side of the entrance side mirror 16a with the acoustooptic medium unit 2 interposed therebetween, and the -1 diffracted beam 8a, the 0 diffracted beam 8b, and the +1 diffracted beam 8c transmitted through the acoustooptic medium unit 2. Is incident on the imaging optical system 3 after being reflected by the exit side mirror 16b. The imaging unit 4 detects the diffracted light that has passed through the imaging optical system 3.

At the time of imaging, the ultrasonic source 5 is arranged so as to be in contact with the object 6 and outputs the ultrasonic wave 7 to the inside of the object 6. The acoustooptic medium unit 2 is disposed so as to be in contact with the object 6 at the time of imaging, and takes in the scattered ultrasonic waves 7 a generated in the object 6.

In the acousto-optic medium part 2, the wedge light beam 8 incident from the wedge light source 1 acts on the scattered ultrasonic wave 7b taken into the acousto-optic medium part 2, whereby the −1st order diffracted light beam 8a and the 0th order diffracted light beam 8b. + 1st order diffracted light beam 8c is generated. The −1st order diffracted light beam 8a, the 0th order diffracted light beam 8b, and the + 1st order diffracted light beam 8c transmitted through the acoustooptic medium unit 2 enter the imaging optical system 3, and only the −1st order diffracted light beam 8a or the + 1st order diffracted light beam 8c. Enters the imaging unit 4.

According to the acousto-optic imaging device 102 according to the present embodiment, the wedge light beam 8 enters and exits the acousto-optic medium unit 2 via the incident-side mirror 16a and the exit-side mirror 16b. The system 3 and the imaging unit 4 can be arranged at a position other than a straight line across the acoustooptic medium unit 2. Therefore, the degree of freedom in optical design is increased, and a smaller image pickup apparatus can be provided.

In the present embodiment, the optical element that gives the light intensity distribution to the wedge light beam 8 may be the neutral density filter 14 or the magnifying optical system 11 having the attenuation factor distribution shown in FIGS. A distribution may be given to the reflectance of the incident side mirror 16a to give a light intensity distribution in the y direction of the wedge light beam 8 in the acoustooptic medium unit 2.

The acousto-optic imaging device disclosed in the present application is useful as a probe for an ultrasonic diagnostic apparatus because it can acquire an ultrasonic image as an optical image. Moreover, since the ultrasonic wave radiated from the vibrating object can be observed as an optical image, it can be applied to uses such as a nondestructive vibration measuring apparatus.

1: wedge light source 2: acousto-optic medium unit 3: coupled lens system 4: imaging unit 5: ultrasonic source 6: object 7: ultrasonic wave 8: wedge beam 9: focal plane 10: laser light source 11: magnifying optical system 12: Optical aperture 13: first cylindrical lens 14: neutral density filter 15 having attenuation factor distribution: light shielding part 16a: incident side mirror 16b: emission side mirror 3a: second cylindrical lens 3b: third cylindrical lens 51: super Acoustic wave signal source 6a: object 7a: scattered ultrasonic wave 7a ': transmitted ultrasonic wave 7b: ultrasonic wave 8a: -1st order diffracted light beam 8b: 0th order diffracted light beam 8c: + 1st order diffracted light beam 81: monochromatic light beam 82, 83: plane wave Luminous flux

Claims

An ultrasonic source that outputs ultrasonic waves;
An acousto-optic medium unit that has an acoustic aperture, and the scattered ultrasound generated by scattering of the ultrasonic wave inside the object enters and propagates from the acoustic aperture;
A wedge light source that emits a monochromatic wedge light beam incident on the acoustooptic medium portion non-parallel to the direction in which the scattered ultrasound propagates;
An imaging optical system on which the diffracted light generated by the change in refractive index generated in the acousto-optic medium unit due to propagation of the scattered ultrasonic wave is incident;
An imaging unit that takes an image of the diffracted light formed by the imaging optical system and outputs an electrical signal;
With
The wedge light beam forms a focal point in a first cross section parallel to the propagation direction of the wedge light beam and the propagation direction of the scattered ultrasonic wave in the acoustooptic medium portion, and is a second cross section perpendicular to the first cross section. In parallel propagation without focusing,
The focal point of the wedge light beam in the first cross section is located between the acoustooptic medium part and the imaging optical system,
The acousto-optic imaging device, wherein the light intensity of the wedge luminous flux in the direction in which the scattered ultrasonic wave propagates in the acousto-optic medium section monotonously increases according to the distance from the acoustic aperture.
The acousto-optic imaging device according to claim 1, wherein a distribution of light intensity in a direction in which the scattered ultrasonic wave propagates of the wedge light beam is defined by an exponential function.
The acousto-optic imaging device according to claim 1, wherein a distribution of light intensity in a direction in which the scattered ultrasonic wave propagates of the wedge light beam is defined by a linear function with respect to a distance from the acoustic aperture.
2. The acousto-optic imaging device according to claim 1, wherein a distribution of light intensity in a direction in which the scattered ultrasonic wave propagates of the wedge light beam is defined by a quadratic function with respect to a distance from the acoustic aperture.
2. The acousto-optic imaging device according to claim 1, wherein a distribution of light intensity in a direction in which the scattered ultrasonic wave propagates of the wedge light beam is defined by a cubic function with respect to a distance from the acoustic aperture.
The distribution of the light intensity in the direction of propagation of the scattered ultrasound of the wedge luminous flux is defined by the power function of the distance from the acoustic aperture or the sum of the power function,
The exponent of the power function is an arbitrary real number.
The acousto-optic imaging device according to claim 1.
The wedge light source is
A laser light source that emits a monochromatic light wave;
A magnifying optical system that receives a monochromatic light wave from the laser light source and emits an enlarged plane wave light beam; and
A cylindrical lens on which a plane wave light beam emitted from the magnification optical system is incident;
An optical element disposed between the laser light source and the magnifying optical system, or between the magnifying optical system and the acoustooptic medium unit, and having a light transmittance having a distribution in a direction in which the scattered ultrasonic wave propagates. Elements,
Including
The cylindrical lens has a refractive power for focusing in the first direction on a plane perpendicular to the propagation direction of the incident plane wave light beam, and has no refractive power in the second direction perpendicular to the first direction.
The first direction of the cylindrical lens is parallel to a direction in which the scattered ultrasound propagates;

The acousto-optic imaging device according to claim 1.
The acousto-optic imaging device according to claim 7, wherein the optical element is a neutral density filter.
The acoustooptic imaging apparatus according to claim 7, wherein the optical element is a liquid crystal element capable of controlling transmittance in a direction in which the scattered ultrasonic wave propagates.
The wedge light source is
A laser light source that emits a monochromatic light wave;
A magnifying optical system that receives a monochromatic light wave from the laser light source and emits an enlarged plane wave light beam, and includes a lens configured to obtain an intensity having a distribution in a direction in which the scattered ultrasonic wave propagates Magnifying optics,
Including a cylindrical lens on which a plane wave light beam emitted from the magnification optical system is incident,
The cylindrical lens has a refractive power for focusing in the first direction on a plane perpendicular to the propagation direction of the incident plane wave light beam, and has no refractive power in the second direction perpendicular to the first direction.
The acousto-optic imaging device according to claim 1, wherein a first direction of the cylindrical lens is parallel to a direction in which the scattered ultrasonic wave propagates.
The acoustooptic imaging apparatus according to any one of claims 7 to 10, further comprising an optical aperture disposed between the magnifying optical system and the cylindrical lens.
The ultrasonic source and the acousto-optic medium part are directed to the object so that the generated scattered ultrasound is incident on the acousto-optic medium part from the acoustic aperture by the ultrasonic wave passing through the object. The acousto-optic imaging device according to claim 1, which is arranged.
The ultrasonic source and the acousto-optic medium part are directed to the object so that the generated scattered ultrasound enters the acousto-optic medium part from the acoustic aperture by reflecting the ultrasonic wave on the object. The acousto-optic imaging device according to claim 1, which is arranged.
An incident side mirror that reflects a wedge light beam emitted from the wedge light source and enters the acoustooptic medium unit;
The acoustooptic imaging apparatus according to any one of claims 1 to 13, further comprising: an exit-side mirror that reflects the diffracted light generated in the acoustooptic medium unit and enters the imaging optical system.
The signal processing part which receives the said electrical signal from the said imaging part, and adjusts the said image so that the brightness nonuniformity in the direction which the said scattered ultrasound wave propagates on the image of the image | photographed image is further provided. The acousto-optic imaging device according to any one of 1 to 14.